I'm sure it would cost millions to digitize the entire collection, not forgetting the outtakes and creating a digital catalog of the paper catalog. Given how much use the collection gets now I imagine a purely economic arguement could justify doing so, in terms of lowering costs to documentary makers.
But those benefits are peanuts compared to the non-direct economic benefits that would result. The potential educational, research and remix uses of the collection are vast. The collection has already given much to our culture, opening it up to orders of magnitudes more users would be a great gift.